Collagenous crystalloids in myoepithelial carcinoma: report of a case and review of the literature.

Since the first report of "tyrosine crystals" in a parotid mixed tumor by Bullock in 1953, authors have described several types of crystalloids in association with mixed tumor and related neoplastic and nonneoplastic entities. The principal classes of these include tyrosine-rich crystalloids, collagenous crystalloids, and one class variously referred to as tyrosine-rich crystals, nontyrosine crystalloids, and amylase crystalloids. We report a myoepithelial carcinoma of minor salivary gland origin containing numerous collagenous crystalloids. To our knowledge, this represents the first report of collagenous crystalloids in a case of myoepithelial carcinoma. In addition, we searched our institution's files for cases of pure myoepithelial tumors. No crystalloids of any form were identified in 27 myoepitheliomas and 15 myoepithelial carcinomas. We review the literature on salivary-related crystalloids, and we propose the term oncocyte/cyst-associated crystalloids to encompass the aforementioned third class of crystalloid. Given distinct morphologic and histochemical properties and given relatively limited disease associations, we conclude that in the appropriate clinical context, the identification of these crystalloids can be diagnostically useful.